Business Overview:

The subject of this case study is a United States Military Base comprised of over 5,000 individuals and over 1400 households. The AFB operates a total of 8 industrial coal-fired power plants to support base operations.

The Challenge:

The Air Force Base enlisted the help of an Engineering Firm to determine the most cost effective solution to satisfy emissions requirements and meet the mandates required by the EPA’s new Boiler MATS rule for their eight coal-fired power plants. The Engineering Firm Determined that Dry Sorbent Injection (DSI) was the best and most cost effective solution.

DSI is the process of adding an alkaline material, in this case, Sodium Bicarbonate, into the flue gas stream to react with the acids and capture harmful flue gases to reduce greenhouse gases at the base’s coal-fired power plants. Sodium Bicarbonate (SBC) is delivered with a D90 of 425 microns and needed to be ground to a D90 of 15 microns. The Engineering Firm needed a company able to provide fine grinding equipment capable of these stringent grinding specifications.

In addition to the very fine particle sizing requirements, the equipment also had a very specific upper limit temperature range. If the fine grinding caused a Delta T of 20°F, the material would cake up and coat the inside of the mill, making it inoperable and ceasing operation until the machine could be cleaned and maintained.

The Solution:

Having consulted with the industrial equipment specialists at Prater Industries in the past, the Engineering Firm contacted Fergus Keane, National Sales Manager, to determine the appropriate equipment needed for the DSI application. After requesting several super sacks of SBC, and several extended time run tests, the Prater team determined that the CLM-36 Air Classifying Mill was able to achieve the quality grind and keep the Delta T below the acceptable level, while achieving the very fine grind.

Capable of sizing of 50 mesh to small micron size, the CLM-36 was the best match for this DSI application. The secondary inlet on the CLM-36 provided additional air for an element of cooling, allowing the machine to operate within the Detla T specifications to produce the fine grind. Other benefits include a large access door for quick inspection and cleaning and a screenless grinding chamber to prevent screen damage, wear and binding.

The Result:

The Prater installation of the CLM-36 Air Classifying Mill was completed in the spring of 2014. The equipment is currently operating per in-line milling specifications at the AFB.


Fergus Keane is the National Sales Manager for Prater Industries. As part of his role, he also maintains a direct sales territory working with customers directly to provide them with world class processing solutions. Fergus has an extensive background in providing Process Solutions for over 17 years. Fergus has worked in his current position at Prater since 2010.

At Prater Industries, results come first. Prater has been providing reliable particle management solutions since 1925. The company specializes in an extensive line of equipment and engineered systems including rotary airlocks, fine grinders, classifier mills, lump breakers, hammermills, screeners/separators, and compactors.